Artificial hand with articulated fingers and passively positioned thumb



L. MASON ARTIFICIAL HAND WITH ARTICULATED FINGERS AND PASSIVELYPOSITIONED THUMB May 22, 1951 Filed Oct. 27, 1948 Huazer A. Mnsau,JNVENTOR.

A7 TOQNEK 2,553,827 RS AND May 22, 1951 H. 1.. MASON ARTIFICIAL HANDWITH ARTICULATED FINGE PASSIVELY POSITIONED THUMB 4 Sheets-Sheet 2 FiledOct. 27, 1948 INVENTOR.

May 22, 1951 H. L. MASON ARTIFICIAL HAND WITH ARTICULATED FINGERS ANDPASSIVELY POSITIONED THUMB 4 Sheets-Sheet 3 Filed Oct. 27. 1948 #055271.Mnso/v,

INVENTOR.

H. L. MASON ARTIFICIAL HAND WITH ARTICULATED FINGERS AND PASSIVELYPOSITIONED THUMB May 22, 1951 4 Sheets-Sheet 4 Filed Oct. 27, 1948INVENTOR.

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ArraeA/En Patented May 22, 195 1 ARTIFICIAL HAND WITH ARTICU LATEDFINGERS AND PASSIVELY POSITIONED THUlWB Hubert L. Mason, Long Beach,Calif., assignor to Northrop Aircraft, Inc., Hawthorne, Calif., acorporation of California Application October 27, 1948, Serial No.56,866

4 Claims.

1 The present invention relates to artificial hands, and one of itsgeneral objects is to provide a new and improved hand capable ofgrasping and holding articles of all shapes and sizes in a mannerrealistically duplicating the prehension of the natural hand. A morespecific object is to provide an artificial hand having articulatedfingers which may be closed with an equalized force about an irregularobject, together with an articulated thumb which is mechanically linkedto the fingers so as to close therewith.

Another important object of the invention is to provide an artificialhand having a thumb which is pivoted for passive rotation between theadducted and abducted positions, and which is adapted to be yieldinglyheld in any adjusted position about its pivot axis. In this sameconnection, one of the features of the invention resides in theprovision of a pivoted thumb which is also articulated for flexion andextension, and which is connected to the finger-closin mechanism by anovel system of linkage, whereby the thumb can be flexed and extended atan position about its adduction-abduction axis.

A further object of the invention, in one of its aspects, is theprovision of a novel latch for securing the thumb in the flexedposition, which is releasable by striking the back of the thumb lightlyagainst the body or against any stationary object such as a table,chair, or the like. The advantage of this arrangement is that it enablesthe amputee to change the position of the thumb without requiring theuse of the other hand, which is particularly desirable in the case ofbilateral amputations.

The foregoing and other objects and advantages of the present inventionwill become apparent to those skilled in the art upon consideration ofthe following detailed description of two illustrative embodimentsthereof, reference being had to the accompanying drawings, wherein:

Figure 1 is a partially sectioned top plan view of the preferred form ofthe invention, the palmar cover plate of which has been removed to showthe finger and thumb actuating mechanism;

Figure 2 is a sectional view of the same, taken along the line 22 inFigure 1;

Figure 3 is another sectional view through the hand, taken along theline 33 in Figure 1;

Figure 4 is an enlarged sectional view of the mechanism at the base ofthe thumb, taken at 4-4 in Figure 2;

Figure 5 is a sectional view, taken along the line 5-5 in Figure 1;

Figure 6 is a partially sectioned top plan view of another embodiment ofthe invention;

Figure 7 is a transverse sectional view through the same, taken at 'l!in Figure 6;

Figure 8 is a sectional view taken at 8--8 in Figure 6;

Figure 9 is an enlarged sectional view of the mechanism at the base ofthe thumb, taken at 99 in Figure 7, showing the thumb in the closed, orflexed position; and

Figure 10 is a view similar to- Figure 9, but showing the thumb in theextended position.

The embodiment of Figures 1 to 5, inclusive, will be taken up first, andin these drawings, the

, hand is designated in its entirety by the reference numeral 5. Thehand [5 is seen to comprise a base plate IE, to which a body shell I! isattached, and mounted on the body shell are articulated fingers l8, E9,and 2|, together with the thumb 22, and the actuating mechanismtherefor; the construction and operation of which will be described indetail presently.

The base plate It constitutes the wrist of the hand and is preferably,although not necessarily, provided with a quick disconnect arrangementof thetype shown and described in the pending application of Gilbert M.Motis, Serial Number 24,598, filed May 1, 1948, now Patent No.2,516,792, and entitled Quick Disconnect Coupling for Artificial Hand orHook, to which reference may be had for full details of construction andoperation. Briefly, the base plate i6 is adapted to be coupled to aoompanionate member on the distal end of a forearm component (notshown), and to this end is provided on its back surface with arearwardly projecting, vertically extending rib 23 having straight andparallel side edges which are provided with outwardly facing flanges 2d.

A shallow, longitudinally extending slot 25 is milled out of the centerof the rib 23, said slot being open at one end and preferably closed atthe other end. A circular hole 26 is provided in the center of the plateIt, and slidably disposed within this hole is a connector 30 which isattached at its front end to the finger closing mechanism. The connector30 extends rearwardly beyond the bottom of the slot 25. and has a radialflange 32 on the end thereof, which is adapted to be received within aslot in the end of a coupling member (not shown) projecting forwardlyfrom the face of an attach plate on the forearm member.

The said attachv plate is companionate to the base plate It, and isformed with channels to receive the flanges 24. The base plate H5 iscoupled to the forearm member by sliding the flanged rib 23 endwise intoa corresponding recess in the attach plate, and then looking the partstogether, for which purpose a springpressed locking pin 33 is providedon the base plate adjacent the top end thereof. The pin 33 is slidablydisposed within a cylindrical bore 34, and is urged outwardly by aspring 35 to seat in a hole in the attach plate. The locking pin 28 isadapted to be disengaged from the attach plate by means of a manuallyoperable handle 36 which projects through a slot 37 in the end of thebase plate I6.

As the base plate approaches its fully seated position, the connector 35is engaged by the aforesaid coupling member on the attach plate, whichis attached to a Bowden cable control wire extending upwardly along thearm. The control wire is attached to a shoulder harness in the usualmanner, and this arrangement causes a pull to be exerted on the controlwire when the harnessed shoulder is shrugged forwardly. From theforegoing it will be seen that the muscular force for operating thefingers and the thumb is transmitted to the actuatin mechanism of thehand by the connector 30, and the latter can therefore be defined as thecontrol member of the hand, by which name it is identified in theclaims.

Projecting forwardly from the base plate It around the outer edgethereof is a flange 33 to which the body shell I! and a palm cover shell39 are attached by means of fiathead machine screws. The body shell I!constitutes the back half of the hand, and is preferably formed of heavygage sheet aluminum or other light metal. The fingers I8, I9, 253 and 2!may be of any desired construction and, as shown herein, each comprisestwo generally tubular sheet metal sections 45 and 4! which are pivotallyjoined together by a pin 42. The base ends of the inner section 49 offingers I8 and I9 are pivotally mounted on a shaft 43, while fingers 20and 2! are pivotally mounted on another shaft 44; the axes of saidshafts being disposed at an angle to one another so that the fingers I8and I9 tend to spread apart from fingers 2c and 2! when extended, and tocome together when closed. The outer ends of the shafts 43 and 44 arereceived within holes in the opposite side walls of the body shell I1,and the inner ends thereof are supported by a central block 45 which isformed on a bracket member 45 mounted on the body plate I'I.

Extending longitudinally through the inner sections of the fingers arelinks 5!], the outer ends of which are attached by pins 5! to the outerfinger sections 4! above the pivot pins 42 (Figure 3), and the innerends of which are attached by pins 52 to bracket 53 mounted on the bodyshell II. Pins 52, it will be noted, are located below the pivot shafts43, 44, which is opposite to the disposition of pins 42, 5!. Link 5!!therefore crosses a line connecting the centers of pins 42 and shafts 43or 44 and by virtue of this arrangement, the outer finger section 4! ispulled inwardly, or in a counterclockwise direction, about its pivot 42when the inner section 40 is swung upwardly about its supporting pivotshafts 43, 44.

Ears 54 project upwardly from the inner finger section above the pivotshafts 43, 44, and connected to these ears by pins 55 are rearwardlyextending links 56, 56. The rear ends of the links 55 for fingers I8 andI9 are connected by pins Bi! to the opposite ends of a transverselydisposed equalizer bar 6!, while the links 55' for fingers 20 and 2| areconnected by pins 52 to another equalizer bar 63. The equalizer bars 6!and 63 are connected at their midpoints by pins 64 and 65 to links 56and 6?, said links extending rearwardly from the equalizer bars andbeing connected by pins I6 and I! to lever arms '12 and I3.

Lever arm I2 is formed integrally with and projects upwardly from atransverse shaft 14 adjacent one end thereof. The ends of the shaft 14are journallecl for rotation in bushings I5 and I6 which are mounted inbearing support blocks l1 and 78, said blocks being secured to theopposite side walls of the body shell ll by fiathead machine screws. Theshaft is supported at its midpoint in another bushing which is mountedin the bracket member 45.

The portion of shaft 14 lying on the side of bracket 45 opposite thelever arm '!2 is reduced slightly in diameter, and mounted side by sideon this reduced portion is a gear sector 8! and sleeve 82. The lever armI3 is formed integrally with the sleeve 82 and projects upwardlytherefrom substantially parallel to lever arm I2. Sleeve 82 and gearsector 8! are fixedly secured to the shaft I4 by pins 83 and 54, andtherefore rotate as one with the shaft.

Meshing with the teeth of gear sector 8! is a worm 85 which is rotatablymounted on an axle 86 projecting upwardly from the base of bracket 46. Apinion 95 is rigidly connected to the worm at the upper end thereof, andmeshes with a rack 9i extending lengthwise of the hand. The back surface52 of rack 5! is smooth and fiat, and bearing on this surface directlyacross from the pinion 90 is a roller 93 turning on an axle 94. Thepurpose of the roller 93 is to back up the rack 9! and hold the latterin mesh with the pinion 95, while at the same time permitting freelongitudinal movement of the rack.

The roller 93 and its axle 94 are supported on a bracket 95, the topportion of which includes a shelf 98 extending laterally across the topof rack 9! and pinion 9B. The axle 86 for the worm 85 and pinion 30extends through a hole in the shelf 95 and has a nut 9! screwed onto theprojecting threaded end thereof. The bottom edge of the rack 95 isslidably supported on another ledge 98 projecting laterally from thebracket 95, and the rack 9! is thus confined against movement relativeto the pinion 95 in the axial direction thereof. Another roller 99turning on a tubular axle I05 alongside the roller 93, also runs on theback surface 52 of the rack, and provides directional stability for therack. The rack 55 is yieldingly urged outwardly, or to the right, asseen in Figure 1, by a spring I5 I, one end of which is anchored to theblock 45, and the other end being attached to the outer end of the rack.

Formed on the rear end of rack 9! is a box I52 which is fixedlyconnected to an arm I53 projecting obliquely from the connector 3!). Therack 9! is thus joined directly to the connector 30 and moves with thelatter as though it were an integral part thereof. One end of a pivotedlever I84 projects into the space between the top and bottom sides ofthe box I92 and is connected thereto by a pin I65, said pin passingthrough a longitudinally extending slot I06 in the lever. The lever I94is swingably supported on a pivot pin Hi3, and its other end isconnected by a pin I I I to a clevis I I 2 screwthreaded on the rear endof a push rod I I3.

The push rod II3 extends forwardly through the pivot center of asupporting structure I I4 for the thumb 22, and is connected at itsfront end to the thumb actuating linkage. The thumb-supporting structureI I4 consists of a base II5 which is secured by flathead machine screwsto the body shell I1, and formed on the upper end of. said base is acircular plate I I6 having a tapped hole I through its center, as shownin Figure 4. An adjusting screw I2I is threaded through the hole I20,and is secured against turning by a set screw I22. The center of thescrew I2I is drilled to provide a hole I23, through which the push rodII3 passes.

Threaded onto the front end of the screw I2I is a radially flangedbearing member I24, upon which is swiveled a turntable I25. Theturntable I comprises a circular plate I26 having a central aperture inwhich the bearing member I24 is received, said aperture being recessedaround its outer edge to provide a seat for the thrust flange I21 of thebearing member. A cylindricalproject into the hollow base section I32 ofthe thumb 22 and are connected therewith by a pivot pin I33. Extensionarms I34 project obliquely forward from the outer ends of the bracketarms I3I, and these are drilled to receive a pin I35 which serves as anaxle for certain elements of the thumb-actuating linkage, which will betaken up in detail presently.

The swiveled plate I26 is spaced a short distance out from thestationary plate H6, and disposed within the space between them is adished spring friction member I36 having a central aperture throughwhich the adjusting screw I2I passes. ber I36 bears against thestationary plate H6, and the outer edge portion thereof bears againstthe adjacent surface of the swiveled plate I26.

The bearing member I24 is adapted to be tightened down on the screw I2Iby means of a spanner wrench (not shown), causing the friction memberI36 to be compressed between the plates I I 6 and I 26. The frictionalresistance to rotation of plate I25 relative to plate H6 is proportionalto the bearing pressure of the member I36 against the plates; hence, thetighter the memberv I36 is compressed, the greater is the resistance,and the more firmly the thumb is held in its angularly adjusted positionabout the pivot axis.

Pivotally connected by a pin I40 to the outer end of the base sectionI32 of the thumb is an outer section I4I, which is likewise formed ofsheet metal. A link I42 is attached at one end by a pin I43 to the outerthumb section I4I adjacent the pivot I40, and the other end of the linkis connected by a pin I44 to one arm of a bell crank I45 which isrotatably supported on the pin I35 between the extension arms I34. Inthe illustrative embodiment, the bell crank I45 is made up of twolaterally spaced side members which are joined together to rotate as oneabout the pivot I35. Rigidly fixed to the bell crank I45 between theside members is a gear sector I46 which meshes with another gear sectorI50. Sector I50 is pivotally supported on the pin I33 between thebracket arms I3I, and is connected to the thumb section I32 by a pinI5I, so that the thumb is constrained to rotate with the sector I50.

The other arm of the bell crank I45 projects laterally inward toward thecenter of the hand,

The center portion of the friction memand is connected by a pin I52 to abracket I53 projecting radially from a sleeve member I54 on the push rodH3. The sleeve member I54 is free to rotate on the push rod, but isconfined against axial movement with'respect thereto by, a radial flangeI55 on the push rod which engages one end of the sleeve. The other endof the sleeve is engaged by a nut I55 which is screwed onto thread I50on the end of the push rod.

The fingers and thumb are pulled closed, or flexed in prehension, whenthe connector 30 is pulled rearwardly by a shrug of the harnessedshoulder. Such rearward movement of the connector 30 causes the rack 9|to move rearwardly with it, which drives the pinion 90 and worm 85.Rotation of the worm drives the gear sector 0! and shaft 14 in acounterclockwise direction. as viewed in Figure 3, thereby swinging thetwo lever arms i2 and 13 rearwardly. Links 65 and 51 are carriedrearwardly with the lever arms 12, 13, and the tensile force transmittedby each of the links is distributed equally by the equalizer bars BI, 63to the fingers to close the same.

Rearward movement of the rack 96 also causes the lever I04 to rock in acounterclockwise direction about its pivot IIO, which causes push rodII3 to be pushed forwardly through the thumbsupporting structure H4.Forward movement of the push rod I I3 rocks the bell crank I 25 and gearsector I46 in a clockwise direction, which drives the gear sector I50 ina counterclockwise direction to close the thumb.

The thumb 22 is adapted to be moved to any desired position about thepivot axis of the rotatable plate I26 between the adducted position,shown in phantom lines in Figure 2, and the abducted position, shown insolid lines in Figure 2.. This pivot axis thus represents theadduction-- abduction axis of the thumb; while the pivot pin I33represents the fiexion-extension axis of the thumb. The thumb isyieldingly held in its angularly adjusted position about theadductionabduction axis by means of the friction member I36, and theamount of frictional resistance to rotation of the thumb is determinedby the extent to which the friction member is compressed.

The other embodiment of the invention, shown in Figures 6 to 10,inclusive, is generally similar in construction to the previouslydiscussed embodiment, and parts that are similar to those alreadydescribed are given the same reference numerals with the suffix a. Thefinger-closing mechanism differs from that of the previous embodiment inthat the shaft 14a is provided with an upwardly extending arm 510 whichis connected by a pin I1I to the front end of a link I12. The rear endof the link 512 is provided with a clevis I13 which receives a tongue414 projecting forwardly from the end of the connector 300., and isconnected therewith by a pin I15. A spring H3 which is anchored at oneend to the bracket 53a of finger 20a, is attachedat its other end to armI10 and exerts a Dull thereon tending to restore the fingers to thenormally extended condition shown in the drawings.

When the connector 30a is pulled rearwardly by a shoulder shrug, theshaft 14a is rocked in a counterclockwise direction, as viewed in Figure8, drawing the fingers ciosed with an equalized pull. When the force onthe connector 30a is relaxed, the shaft 14a is rocked back to itsinitial position by the spring I16, opening the fingers out to theextended position.

The thumb 22a is swiveled for rotation about the adduction-abductionaxis between the two 7 positions shown in Figure '7, and is pivoted alsofor swinging movement about the fiexion-extension axis, represented bythe pin 133a. The thumb itself, however, is made in one piece, withoutthe joint shown in the preceding embodiment, and is not adapted to beclosed by the operation of the connector 3%. Instead, the thumb ispassively changed from the extended position shown in Figure to theflexed position shown in Figure 9, and is releasably held in the latterposition by latching mean which will be described presently.

The thumb 22a is supported on a stationary standard I88 which is fixedto the body shell Ha,

and formed on the upper end of the standard is a circular boss |8ihaving a central hole I82. Extending through the hole E82 is a bolt I83,the threads of which are screwed into a tapped hole I84 of a rotatablemember 185. Interposed between the head lts of the bolt 1&3 and the adbjacent face of the stationary boss I8! is a resilient friction disk I933of cork or like material, while another friction disk 95 is interposedbetween the adjacent faces of the rotatable member H and stationary bosslei When the screw I83 is tightened, the disks H98 and i9! arecompressed, increasing the frictional resistance to turning of themember 35 with respect to member [8 i.

Laterally spaced bracket arms I92 project radially outward from one sideof the member I85, and pass on opposite sides or" the thumb 2211; theends of pivot pin I33a being received within holes in the said arms. Atorsion spring 21! is wrapped around the pin 533a and one end thereof isanchored at 2 i 2 in the member 585. The other end of the spring bearsagainst the thumb 22a urging the latter outwardly toward the extendedposition shown in Figure 10.

The thumb is adapted to be latched in the flexed position shown inFigure 10, and to this end is provided with a catch 193 which is securedby rivets 594 to the thumb. A lip i9?) on the outer end of the catchi933 is adapted to be engaged by another lip we on a detent 253, andwhen thus engaged, locks the thumb in the flexed position until the lip9 3 is disengaged from lip Extending through a hole in detent 255 andprojecting laterally from opposite sides thereof is a pin 28%, the endsof which are slidably disposed within slots 262 in bracket members 199,said bracket members being formed integrally with the member 585 andprojecting from one end thereof. A leaf spring 2% is secured to themember I85 by pressed-in rivets 255, and a rolled lip 204 on the springbears downwardly against the top of the detent 295.

When pin 231 is at the bottom of slot 202, the spring lip 2M engages thedetent Ziill above the pin, exerting a counterclockwise torque on thedetent. When pin 2M is at the top of slot 202, the spring lip 26:?engages the detent below the pin and exerts a clockwise torque thereon.A limit stop pin 2% limits the counterclockwise rotation of detent 28bto the position shown in Figure 10.

If the thumb and latch detent are in the positions shown in Figure 10,the thumb is closed to the flexed position and locked in place by merelystriking the back of the thumb lightly against the body, or anyconvenient object such as a table top, chair, or the like. As the thumbswings upwardly, or counterclockwise about pivot l33a, the end of catchI95 engagesa shoulder! Ill-on detentifiil, pushing the latter inwardlyuntil pin 20! reaches the top of slot 202. At this point, the spring 263urges the detent down into engagement with the catch, with the resultthat the lip see remains interlocked with lip 195 when the presur-e isremoved from the back of the thumb. Spring 2!! now pulls the thumb outto the position shown in Figure 9, with pin 20] at the bottom of slot2&2. The interlocking engagement of the lips I95, 19-3 prevents thedetent 2% from yielding to the spring 293 and swinging about pin Ziii tothe limit stop 2%. However, the next time that pressure is applied tothe back of the thumb, the lip is disengaged from lip 55 and detent2E3?) snaps back against the limit stop. The advantage of thisarrangement will be readily apparent to those skilled in the art, sinceit enables the amputee to change the position of the thumb without usingthe other hand or hook.

While I have shown and described in consider able detail twoillustrative embodiments of my invention, it is to be understood thatsuch details are not restrictive, and that various changes may be madein the shape and arrangement of the several parts without departing fromthe broad scope of the invention, as defined in the appended claims.

I claim:

1. In an artificial hand, the combination of a plurality of articulatedfingers and an articulated thumb, said thumb being swiveled for rotationabout an adduction-abduction axis, a forcetransmitting control member,linkage means operatively connected to said control member for closingsaid fingers with an equalized force, and for closing said thumb, saidlinkage means for closing said thumb including an axially movable pushrod disposed coaxial with the swivel axis of the thumb.

2. In an artificial hand, the combination of a plurality of fingers andan articulated thumb, said thumb being swiveled for rotation about anadduction-abduction axis, a force transmitting control member, linkagemeans operatively connecting said control member to said thumb forciosing the same, said linkage means including an axially movable pushrod disposed coaxial with said adduction-obduction axis, and a memberjournaled on said push rod for rotation about the axis thereof butconstrained against axial movement with respect thereto, said memberbeing connected to a portion of said linkage means mounted on said thumband rotatable therewith, whereby said thumb can be closed by saidlinkage means in all positions about said adduction-abduction axis.

3. In an artificial hand having a plurality of fingers and a :thumb, thecombination of a thumb-supporting plate swiveled on said hand forrotation about an adduction-abduction axis, said thumb being pivotallysupported on said plate fcrswinging movement about a fiexion-extensionaxis, a force transmitting control member, linkage means operativelyconnecting said control member to said thumb for swinging the same aboutsaid flexion-extension axis, said linkage means'including an axiallymovable push rod extending through said plate coaxial with saidadduction-abduction axis, a gear sector fixed to said thumb concentricwith said fiexion-extension axis, another gear sector pivotallysupported on said plate-and -meshing with said first-named sector,anda-lever arm fixed to said last-named sector and-connected to saidpush rod, whereby axialmovementof -said push rod causes saidlastarticulated fingers and an articulated thumb, a 5

force-transmitting control member, a longitudinally movable rackconnected to said control member, a rotatable pinion meshing with saidrack, a worm fixedly connected to said pinion to rotate therewith, agear sector meshing with said worm, said gear secto-r being fixedlymounted on a transversely disposed, rotatable shaft, a pair of armsprojecting from said shaft, forwardly extending links connected to saidarms, each of said links being connected to the midpoint of an equalizerbar, and other links connecting the two ends of each equalizer bar totwo of said fingers, whereby an equalized force is transmitted to thetwo fingers associated with each equalizer bar, and means connected tosaid control member for closing said thumb simultaneously with saidfingers.

HUBERT L. MASON.

REFERENCES CITED 'The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 760,102 Carnes May 1'7, 19041,046,966 Carnes Dec. 10, 1912 1,324,564 Pringle Dec. 9, 1919 152,464,577 Hobbs Mar. 15, 1949 FOREIGN PATENTS Number Country Date345,340 Great Britain Mar. 20, 1931

